Poly(trimethylene-ethylene ether) glycols

ABSTRACT

A poly(trimethylene-ethylene ether)glycol is disclosed. The poly(trimethylene-ethylene ether)glycol is, preferably, prepared by the polycondensation of 1,3-propanediol reactant and ethylene glycol reactant. The composition is preferably used in breathable membranes, synthetic lubricants, hydraulic fluids, cutting oils, motor oils, surfactants, spin-finishes, water-borne coatings, laminates, adhesives, packaging, films and foams, fibers and fabrics.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/621,892, filed Jul. 17, 2003, abandoned, which claims the prioritybenefit of U.S. Provisional Application Ser. No. 60/402,262, filed Aug.9, 2002.

FIELD OF THE INVENTION

This invention relates to polyether glycols, in particular,poly(trimethylene-ethylene ether)glycols and their manufacture and use.

BACKGROUND OF THE INVENTION

Polytrimethylene ether glycol (“PO3G”) and its use have been describedin a number of patents and patent applications. PO3G can be prepared bydehydration of 1,3-propanediol or by ring opening polymerization ofoxetane. PO3G can be prepared from 1,3-propanediol, preferably asdescribed in U.S. Published patent application Nos. 2002/7043 A1 and2002/10374 A1, both of which are incorporated herein by reference.

U.S. Published patent application No. 2002/7043 A1 teaches that thereaction mixture can comprise up to 50 mole %, preferably 1 to 20 mole%, based on all diols present, of a comonomer diol other than oligomersof 1,3-propanediol. Listed are 2-methyl-1,3-propanediol,2,2-dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol,1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol andmixtures thereof. More preferred as comonomers are2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, and2,2-diethyl-1,3-propanediol.

Similarly, U.S. Published patent application No.2002/10374 A1 teachesthat the reaction mixture can comprise up to 50 mole %, preferably 1 to20 mole %, based on all diols present, of a comonomer diol other thanoligomers of 1,3-propanediol. Listed are aliphatic diols, for example1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol,1,10-decanediol, 1,12-dodecanediol,3,3,4,4,5,5-hexafluro-1,5-pentanediol,2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol,3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10-hexadecafluoro-1,12-dodecanediol,cycloaliphatic diols, for example 1,4-cyclohexanediol,1,4-cyclohexanedimethanol and isosorbide, polyhydroxy compounds, forexample glycerol, trimethylolpropane, and pentaerythritol. A preferredgroup of comonomer diol is selected from the group consisting of2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol,2,2-diethyl-1,3-propanediol, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol,1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, isosorbide, andmixtures thereof.

Polyether ester elastomer comprising polytrimethylene ether ester softsegment and tetramethylene and trimethylene ester hard segments aredescribed in U.S. Pat. No. 6,562,457 B1 and U.S. Published PatentApplication No. 2003/120026 A1, both of which are incorporated herein byreference. Polytrimethylene ether ester amides are described in U.S.Pat. No. 6,590,065 B1, which is incorporated herein by reference.Polyurethanes and polyurethane ureas are described in U.S. patentapplication ser. No. 10/215,575, filed Aug. 9, 2002 (published as US2004-0030060 A1), which is incorporated herein by reference.

Polytrimethylene ether glycol is preferably prepared by polycondensationof 1,3-propanediol, preferably using an acid catalyst as described inU.S. Published Patent Application Nos. 2002/7043 A1 and 2002/10374 A1.Polyethylene glycol, on the other hand, is made from the ring-openingpolymerization of ethylene oxide, and can not be polymerized fromethylene glycol by acid catalyzed polycondensation due to thecyclization of its dimer into dioxane.

SUMMARY OF THE INVENTION

The invention is directed to poly(trimethylene-ethylene ether) glycol,its manufacture and use. The poly(trimethylene-ethylene ether) glycolpreferably has a molecular weight of 250 to about 10,000, morepreferably of at least about 1,000 to about 5,000. According to oneaspect, a composition comprises poly(trimethylene-ethylene ether) glycoland additive. Preferably, the additive comprises at least one each of atleast one of delustrant, colorant, stabilizer, filler, flame retardant,pigment, antimicrobial agent, antistatic agent, optical brightener,extender, processing aid, viscosity booster and mixtures thereof.

The poly(trimethylene-ethylene ether) glycol is preferably prepared bypolycondensation of 1,3-propanediol reactant and ethylene glycolreactant. Preferably, the 1,3-propanediol reactant is selected from thegroup consisting of 1,3-propanediol, and oligomers of 1,3-propanediolhaving a degree of polymerization of 2 to 3, and mixtures thereof.Preferably, the ethylene glycol reactant is selected from the groupconsisting of ethylene glycol, and oligomers of ethylene glycol having adegree of polymerization of 3 to 4, and mixtures thereof. Morepreferably the poly(trimethylene-ethylene ether) glycol is prepared bythe polycondensation of 1,3-propanediol and ethylene glycol.

Preferably the polycondensation is carried out with an acidpolycondensation catalyst. Preferably, the polycondensation catalyst ishomogeneous, preferably sulfuric acid.

In accordance with one aspect, the poly(trimethylene-ethylene ether)glycol is prepared by a process comprising the steps of:

-   -   (a) providing (1) 1,3-propanediol reactant, (2) ethylene glycol        reactant and (3) and acid polycondensation catalyst; and    -   (b) polycondensing the 1,3-propanediol and ethylene glycol        reactants in the presence of the acid polycondensation catalyst        to form poly(trimethylene-ethylene ether) glycol.

In accordance with another aspect, the poly(trimethylene-ethylene ether)glycol is prepared by a continuous process comprising:

-   -   (a) continuously providing (i) 1,3-propanediol reactant, (ii)        ethylene glycol reactant and (iii) acid polycondensation        catalyst; and    -   (b) continuously polycondensing the 1,3-propanediol and ethylene        glycol reactants in the presence of the acid polycondensation        catalyst to form poly(trimethylene-ethylene ether) glycol.

In accordance with another aspect, the poly(trimethylene-ethylene ether)glycol is prepared by a semi-continuous process comprising the steps of:

-   -   (a) batch polycondensing 1,3-propanediol reactant in the        presence of acid polycondensation catalyst; and    -   (b) adding ethylene glycol reactant to the batch polycondensing        over time.

According to one embodiment, the poly(trimethylene-ethylene ether)glycol is a block copolymer of polyethylene oxide and polytrimethyleneoxide. Preferably, the molecular weight of the block copolymer is atleast about 1000, preferably up to about 20,000.

In accordance with another embodiment, the poly(trimethylene-ethyleneether) glycol is used in at least one of breathable membranes, syntheticlubricants, hydraulic fluids, cutting oils, motor oils, surfactants,spin-finishes, water-borne coatings, laminates, adhesives, packaging,films and foams, fibers and fabrics. Preferably thepoly(trimethylene-ethylene ether) glycol is used as a base polymer insynthetic lubricants and spin finish formulations and in water-bornecoatings.

According to another aspect of the present invention, thepoly(trimethylene-ethylene ether) glycol is used as a soft segment tomake block copolymers.

In one embodiment, the block copolymers comprise blockpoly(trimethylene-ethylene ether) ester as a soft segment with apolymeric hard segment. The preferred polymeric hard segment is selectedfrom esters and amides.

The polyether esters are preferably thermoplastic elastomer, preferablycomprising C₂ to C₁₂ alkylene ester as the hard segment. These polyetheresters preferably comprise about 90 to about 10 weight %poly(trimethylene-ethylene ether) glycol soft segment and about 10 toabout 90 weight % alkylene ester hard segment, based on the total amountof hard and soft segments. Also preferably, the mole ratio of hardsegment to soft segment is at least about 2.0, more preferably, about2.0 to about 4.5.

The polyether esters can be prepared by providing and reacting

-   -   (a) poly(trimethylene-ethylene ether) glycol,    -   (b) at least one diol, and    -   (c) at least one of dicarboxylic acid, ester, acid chloride and        acid anhydride.

The polyether esters can also be prepared by providing and reacting:

-   -   (a) poly(trimethylene-ethylene ether) glycol, and    -   (b) at least one polyester.

Another aspect in accordance with the present invention relates to fiberprepared from a poly(trimethylene-ethylene ether) glycol soft segmentand alkylene ester hard segment. A further aspect relates to fabric madefrom the fiber. A still further aspect relates to films and membranesmade from the block copolymer.

The poly(trimethylene-ethylene ether) amide is also preferably athermoplastic elastomer. Preferably it comprises polyamide hard segmentsjoined by ester linkages to poly(trimethylene-ethylene ether) softsegments. Preferably, the polyamide hard segment is the reaction productof carboxyl terminated polyamide or diacid anhydride, diacid chloride ordiester acid equivalent thereof.

In a further aspect, a polyurethane or polyurethane urea (thermoplasticelastomer) comprises poly(trimethylene-ethylene ether) as a softsegment. Preferably, the hard segment comprises polyurethane orpolyurethane urea. The polyurethane/polyurethane urea preferablycomprises less than 90 weight %, more preferably less than about 70weight %, or less than about 50 weight % soft segment. Additionaldetails regarding the polyurethane/polyurethane urea hard segment aredescribed in pending U.S. application Ser. No. 10/215,575, filed Aug. 9,2002 (published as US 2004-0030060 A1), which is incorporated herein byreference in its entirety.

DETAILED DESCRIPTION OF THE INVENTION

Unless otherwise stated, all percentages, parts, ratios, etc., are byweight.

Further, when an amount, concentration, or other value or parameter isgiven as either a range, preferred range or a list of upper preferablevalues and lower preferable values, this is to be understood asspecifically disclosing all ranges formed from any pair of any upperrange limit or preferred value and any lower range limit or preferredvalue, regardless of whether ranges are separately disclosed.

The invention is directed to poly(trimethylene-ethylene ether) glycols.The poly(trimethylene-ethylene ether) glycol has a number averagemolecular weight (Mn) of at least 250, preferably at least about 500,more preferably at least about 1,000, even more preferably at leastabout 1,500 and most preferably about 2,000. The Mn is preferably up toabout 10,000, more preferably up to about 5,000, even more preferably upto about 4,000, yet even more preferably up to about 3,000, and morepreferably up to about 2,500. Reference herein to molecular weight,unless otherwise indicated is to Mn.

The poly(trimethylene-ethylene ether) glycol is preferably prepared from1,3-propanediol reactant and ethylene glycol reactant. It is preferablyprepared by polycondensation of 1,3-propanediol reactant and ethyleneglycol reactant, more preferably by the polycondensation of1,3-propanediol and ethylene glycol.

By “1,3-propanediol reactant” is meant 1,3-propanediol, its dimers, andtrimers, and mixtures thereof. In addition, “polytrimethylene etherglycol” and “poly(trimethylene-ethylene ether) glycol” are used to referto polymers having a Mn of 250 or more.

By “ethylene glycol reactant” is meant ethylene glycol, and its trimersand tetramers. In addition, “polyethylene glycol” is used to refer topolymers having a Mn of 250 or more. Diethylene glycol will cyclize todioxane during acid catalyzed polycondensation and, therefore, itspresence should preferably be kept to a minimum.

Preferably the 1,3-propanediol reactant is selected from the groupconsisting of 1,3-propanediol, and oligomers of 1,3-propanediol having adegree of polymerization of 2 to 3, and mixtures thereof.

Preferably the ethylene glycol reactant is selected from the groupconsisting of ethylene glycol, and oligomers of ethylene glycol having adegree of polymerization of 3 to 4, and mixtures thereof.

In one preferred embodiment, the 1,3-propanediol reactant is1,3-propanediol.

In one preferred embodiment, the ethylene glycol reactant is ethyleneglycol.

The preferred starting materials for this invention are 1,3-propanedioland ethylene glycol, and in some instances for simplicity, applicantswill refer to 1,3-propanediol and ethylene glycol in describing theinvention. The 1,3-propanediol can be obtained from a petrochemical orrenewable source.

The poly(trimethylene-ethylene ether) glycols are preferably preparedusing at least about 1 mole %, preferably at least about 2 mole % andmore preferably at least about 10 mole %, and preferably up to about 50mole %, more preferably up to about 40 mole %, and most preferably up toabout 30 mole %, of ethylene glycol reactant based on the total amountof 1,3-propanediol reactant and ethylene glycol reactant. Thepoly(trimethylene-ethylene ether) glycols are preferably prepared usingup to about 99 mole %, preferably up to about 98 mole %, and preferablyat least about 50 mole %, more preferably at least about 60 mole %, andmost preferably at least about 70 mole %, of 1,3-propanediol reactantbased on the total amount of 1,3-propanediol reactant and ethyleneglycol reactant.

The process can be batch, semi-continuous, continuous, etc., and theethylene glycol can be added prior to or during the reaction. Thepoly(trimethylene-ethylene ether) glycols of the invention arepreferably prepared using the methods described in U.S. Published PatentApplication Nos. 2002/7043 A1 and 2002/10374 A1, both of which areincorporated herein by reference in their entireties, with furtherreaction of the ethylene glycol with the 1,3-propanediol reactant.

Thus, in one preferred embodiment, the poly(trimethylene-ethylene ether)glycol is prepared by a process comprising the steps of: (a) providing(1) 1,3-propanediol reactant, (2) ethylene glycol reactant and (3) acidpolycondensation catalyst; and (b) polycondensing the 1,3-propanedioland ethylene glycol reactants to form a poly(trimethylene-ethyleneether) glycol. Preferably, the reaction is conducted at elevatedtemperatures for example about 150 to about 210° C., and preferably atatmospheric pressure or preferably at less than one atmosphere pressure.In one preferred embodiment thereof, the process comprises the steps of:(a) providing 1,3-propanediol, ethylene glycol and acid polycondensationcatalyst; (b) condensing 1,3-propanediol and ethylene glycol reactantsto form oligomers or prepolymers thereof having an average degree ofpolymerization of 2 to 20, preferably 2 to 9, or a mixture comprisingone or more thereof; and (c) polycondensing the oligomer or prepolymeror mixture to form a poly(trimethylene-ethylene ether) glycol atatmospheric inert gas pressure or less than one atmosphere pressure orat atmospheric pressure in an inert atmosphere, preferably nitrogen.Preferably step b) is carried out at about atmospheric pressure, thepressure in step c) is less than 300 mm Hg (40 kPa), the temperature instep b) is about 150 to about 210° C. and the temperature in step c) isabout 150 to about 250° C.

The poly(trimethylene-ethylene ether) glycols of the present inventioncan be produced continuously using the procedure of U.S. PublishedPatent Application No. 2002/10374 A1. Thus, in another preferredprocess, the poly(trimethylene-ethylene ether) glycol is prepared by acontinuous process comprising: (a) continuously providing (i)1,3-propanediol and ethylene glycol reactants, and (ii) polycondensationcatalyst; and (b) continuously polycondensing the reactants to formpoly(trimethylene-ethylene ether) glycol. Preferably the polycondensingis carried out in two or more reaction stages. Preferably thepolycondensing is carried out at a temperature greater than about 150°C., more preferably greater than about 180° C. and preferably less thanabout 250° C., more preferably less than about 210° C. Preferably thepolycondensation is carried out at a pressure of less than oneatmosphere, preferably at least about 50 mm Hg. In one preferredcontinuous process the polycondensation is carried out in an up-flowco-current column reactor and the 1,3-propanediol reactant, ethyleneglycol reactant and poly(trimethylene-ethylene ether) glycol flow upwardco-currently with the flow of gases and vapors, preferably where thereactor has 3 to 30 stages, more preferably 8 to 15 stages. The1,3-propanediol reactant can be fed to the reactor at one or multiplelocations. In another preferred embodiment, the polycondensation iscarried out in a counter current vertical reactor wherein the1,3-propanediol and ethylene glycol reactants andpoly(trimethylene-ethylene ether) glycol flow in a mannercounter-current to the flow of gases and vapors. Preferably the reactorhas two or more stages. Preferably the 1,3-propanediol reactant andethylene glycol reactant are fed at the top of the reactor, andpreferably the ethylene glycol reactant is also fed at multiplelocations to the reactor. In yet another preferred embodiment, thepolycondensation is first carried out in at least one prepolymerizerreactor and then continued in a column reactor, the 1,3-propanediolreactant comprises 90 weight % or more 1,3-propanediol and the ethyleneglycol reactant comprises 90 weight % or more ethylene glycol, and inthe prepolymerizer reactor the 1,3-propanediol is polymerized with thecatalyst to a degree of polymerization of at least 5. Most preferably,in the at least one prepolymerizer reactor the 1,3-propanediol andethylene glycol are polymerized with the catalyst to a degree ofpolymerization of at least 10 and the column reactor comprises 3 to 30stages. Preferably the at least one prepolymerizer reactor is awell-mixed tank reactor.

In another embodiment, the poly(trimethylene-ethylene ether) glycol isprepared by a semi-continuous process comprising the steps of: (a) batchpolycondensing 1,3-propanediol reactant in the presence of acidpolycondensation catalyst; and (b) adding ethylene glycol reactant tothe batch polycondensing over time.

The polycondensation catalysts preferred for these reactions aredescribed in U.S. Published Patent Application Nos. 2002/7043 A1 and2002/10374 A1. They include homogeneous catalysts such as Lewis Acids,Bronsted Acids, super acids, and mixtures thereof. Examples includeinorganic acids, organic sulfonic acids, heteropolyacids, and metalsalts thereof. Preferred are sulfuric acid, fluorosulfonic acid,phosphorus acid, p-toluenesulfonic acid, benzenesulfonic acid,phosphotungstic acid, phosphomolybdic acid, trifluoromethanesulfonicacid, 1,1,2,2-tetrafluoro-ethanesulfonic acid,1,1,1,2,3,3-hexafluoropropanesulfonic acid, bismuth triflate, yttriumtriflate, ytterbium triflate, neodymium triflate, lanthanum triflate,scandium triflate and zirconium triflate. Heterogeneous catalysts, suchas zeolites, fluorinated alumina, acid-treated silica, acid-treatedsilica-alumina, heteropolyacids and heteropolyacids supported onzirconia, titania, alumina and/or silica, can also be used. Preferredare the aforementioned homogeneous catalysts, and most preferred issulfuric acid.

The poly(trimethylene-ethylene ether) glycol prepared from the aboveprocess is optionally purified as described in U.S. Published PatentApplication Nos. 2002/7043 A1 and 2002/10374 A1, or by other means.Sometimes, it is desired to hydrolyze the sulfate ester groups presentin the polymer to improve functionality of the polymer for use as anintermediate in the preparation of thermoplastic elastomers. Thefunctionality of the polymer refers to the number of hydroxyl groups permolecule. In general, the functionality of poly(trimethylene-ethyleneether) glycol is close to 2 because very few polymer molecules maycontain unsaturation ends. Depending upon the application, the watersoluble low molecular weight fraction is either removed from the polymeror retained. The acid present in the polymer is either removed orneutralized with a soluble base. Neutralization with a base isaccompanied by the formation of alkali metal salt. If insoluble base isused to neutralize the acid present in the polymer, the salts formed canbe removed by filtering the polymer.

The conventional additives commonly used in polyether glycols andthermoplastic elastomers can be incorporated into the 1,3-propanediolreactant, the ethylene glycol reactant, the poly(trimethylene-ethyleneether) glycols, and the thermoplastic elastomers and other products madefrom the poly(trimethylene-ethylene ether) glycols, by known techniques.Such additives include delusterants (e.g., TiO₂, zinc sulfide or zincoxide), colorants (e.g., dyes), stabilizers (e.g., antioxidants,ultraviolet light stabilizers, heat stabilizers, etc.), fillers, flameretardants, pigments, antimicrobial agents, antistatic agents, opticalbrighteners, extenders, processing aids, viscosity boosters, and otherfunctional additives. As a specific example, an antioxidant preventsoxidation of polyethers that are subject to oxidation during storage. Apreferred antioxidant stabilizer is butylated hydroxy toluene or BHT,used at a level of about 50 to about 500 micrograms/g based on theweight of the polymer. The most preferred level is about 100micrograms/g.

The invention is also directed to poly(trimethylene-ethylene ether)glycol block copolymer. In one preferred embodiment, the block copolymeris made using polyethylene glycol and polytrimethylene glycol. Thepreferred molecular weight of the block copolymer is at least about1,000, more preferably at least about 2,000, or at least about 4,000.The molecular weight of the block copolymer is preferably up to about20,000, more preferably up to about 10,000, or up to about 5,000.

The weight % of polyethylene glycol used to make the block copolymer isat least about 10%, preferably at least about 20%, or at least about30%, based on the total amount of polyethylene glycol andpolytrimethylene glycol. The weight % of polyethylene glycol in theblock copolymer can be up to about 70%, preferably up to about 50%, orup to about 40%.

Block copolymer can be made in various ways. For example, polyethyleneglycol and polytrimethylene glycol of varying chain lengths can bereacted as described above. Also for example, homopolymer ofpolyethylene glycol can be added to a reactor containing 1,3-propanedioland the mixture reacted in the presence of the acid catalyst, forexample, as described above.

The poly(trimethylene-ethylene ether) glycols can be used in the samemanner as polytrimethylene ether glycols, as well as in otherapplications where these polyether glycols can be tailored to perform.For example, they are useful, as a base polymer in synthetic lubricantssuch as hydraulic fluids, cuffing oils, and motor oils to provide lowfriction/traction. They are also useful as surfactants, spin-finishes,in water-borne coatings, and in making thermoplastic elastomers. Theycan be used in injection molding, blow molding, extrusion andcompression molding, and reactive extrusion in the manufacture ofcoatings, laminates and adhesives, in the manufacture of packaging andindustrial films, in the manufacture of other melt processable products,in the manufacture of foams and cast elastomers, and in the manufactureof fibers and fabrics. Examples of thermoplastic elastomers includepoly(trimethylene-ethylene ether) ester elastomers,poly(trimethylene-ethylene ether) amides, and polyurethane orpolyurethane urea elastomers such as described in the above-referencedU.S. Pat. No. 6,562,457 B1, U.S. Published Patent Application2003/120026 A1, U.S. Pat. No. 6,590,065 B1 and U.S. patent applicationSer. No. 10/215,575 (published as US 2004-0030060 A1).

In another aspect, the invention is directed to polyether estercomprising poly(trimethylene-ethylene ether) ester soft segment(s) andalkylene ester hard segment(s). These are block copolymers, andpreferably are thermoplastic elastomers. They preferably contain C₂ toC₁₂ alkylene ester hard segments, preferably C₂-C₄ alkylene ester hardsegments. Preferred are dimethylene ester, trimethylene ester andtetramethylene ester hard segment, the latter two for example, asdescribed in U.S. Pat. No. 6,562,457 B1 and in U.S. Patent ApplicationPublication No. 2003/120026 A1, both of which are incorporated herein byreference. The preferred polyether ester elastomers, as well as theirpreparation and use, is basically the same as described in U.S. Pat. No.6,562,457 B1 and U.S. Patent Application Publication No. 2003/120026 A1.

The polyether ester elastomer preferably comprises about 90 to about 10weight % poly(trimethylene-ethylene ether) ester soft segment and about10 to about 90 weight % alkylene ester hard segment. They preferablycontain at least about 90 to about 60 weight % ofpoly(trimethylene-ethylene ether) ester soft segment and about 10 toabout 40 weight % alkylene ester hard segment. More preferably, theycomprise at least about 70% or about 74 weight %,poly(trimethylene-ethylene ether) ester soft segment, and preferablycontain up to about 85, more preferably up to about 82 weight %,poly(trimethylene-ethylene ether) ester soft segment. They preferablycontain at least about 15 weight %, more preferably at least about 18weight %, and preferably contain up to about 30 weight %, morepreferably up to about 26 weight %, alkylene ester hard segment.

The mole ratio of hard segment to soft segment is preferably at leastabout 2.0, more preferably at least about 2.5, and is preferably up toabout 4.5, more preferably up to about 4.0.

The polyether ester can be made by providing and reacting (a)poly(trimethylene-ethylene ether) glycol and (b) at least one polyester.Preferably, the polyester is at least one of polyethylene terephthalate,polytrimethylene terephthalate and polytetramethylene terephthalate. Thepolyether ester is preferably prepared by providing and reacting (a)poly(trimethylene-ethylene ether) glycol, (b) diol, preferably1,4-butanediol, 1,3-propanediol or 1,2-ethanediol, and (c) at least oneof dicarboxylic acid, ester, acid chloride or acid anhydride.Preferably, the dicarboxylic acid, ester, acid chloride or acidanhydride is an aromatic dicarboxylic acid or ester, more preferablyselected from the group consisting of dimethyl terephthalate,bibenzoate, isophthlate, phthalate and naphthalate; terephthalic,bibenzoic, isophthalic, phthalic and naphthalic acid; and mixturesthereof. Most preferred are terephthalic acid and dimethylterephthalate. The polyether esters can be made using polycondensationcatalyst, for example, Tyzor® TPT (tetra-isopropoxide titanate), sold byE.I. duPont de Nemours and Company.

The invention is also directed to films, membranes and fibers preparedfrom the polyether ester. Preferred fibers include monocomponentfilament, staple fiber, multicomponent fiber such as bicomponent fiber(containing the polyether ester as at least one component). The fibersare used to prepare woven, knit and nonwoven fabric.

The polyether esters of this invention can be used to prepare meltspinnable thermoplastic elastomers having excellent strength andstretch-recovery properties. The polyether esters of this invention canbe used to prepare membranes having high breathability.

In another embodiment, the invention is directed topoly(trimethylene-ethylene ether)amide comprisingpoly(trimethylene-ethylene ether) soft segment and a polyamide hardsegment. These are, preferably, elastomeric poly(trimethylene-ethyleneether) amides, and are similar to the polytrimethylene ether amidesdescribed in U.S. Pat. No. 6,590,065 B1, which is incorporated herein byreference, and their manufacture and use. These are block polymers. Theycontain poly(trimethylene-ethylene ether) soft segments and polyamidehard segments.

The polyamide segment preferably has an average molar mass of at leastabout 300, more preferably at least about 400. Its average molar mass ispreferably up to about 5,000, more preferably up to about 4,000 and mostpreferably up to about 3,000.

The poly(trimethylene-ethylene ether) ester amide preferably comprises 1up to an average of up to about 60 polyalkylene ether ester amide repeatunits. Preferably it averages at least about 5, more preferably at leastabout 6, polyalkylene ether ester amide repeat units. Preferably itaverages up to about 30, more preferably up to about 25, polyalkyleneether ester amide repeat units.

The weight percent of polyamide segment, also sometimes referred to ashard segment, is preferably at least about 10% and most preferably atleast about 15% and is preferably up to about 60%, more preferably up toabout 40%, and most preferably up to about 30%. The weight percent ofpoly(trimethylene-ethylene ether) segment, also sometimes referred to assoft segment, is preferably up to about 90%, more preferably up to about85%, and is preferably at least about 40%, more preferably at leastabout 60% and most preferably at least about 70%.

The poly(trimethylene-ethylene ether) ester amide preferably comprisespolyamide hard segments joined by ester linkages topoly(trimethylene-ethylene ether) soft segments and is prepared byreacting carboxyl terminated polyamide or diacid anhydride, diacidchloride or diester acid equivalents thereof and polyether glycol underconditions such that ester linkages are formed. Preferably it isprepared by reacting carboxyl terminated polyamide and polyether glycolcomprising at least 50 weight %, more preferably at least 75 weight %,and most preferably about 85 to 100 weight %, poly(trimethylene-ethyleneether) glycol.

In one preferred embodiment the carboxyl terminated polyamide is thepolycondensation product of lactam, amino-acid or a combination thereofwith dicarboxylic acid. Preferably, the carboxyl terminated polyamide isthe polycondensation product of C₄-C₁₄ lactam with C₄-C₁₄ dicarboxylicacid. More preferably, the carboxyl terminated polyamide is thepolycondensation product of lactam selected from the group consisting oflauryl lactam, caprolactam and undecanolactam, and mixtures thereof,with dicarboxylic acid selected from the group consisting of succinicacid, adipic acid, suberic acid, azelaic acid, sebacic acid,undecanedioic acid, dodecanedioic acid, terephthalic acid, andisophthalic acid, and mixtures thereof. Alternatively, the carboxylterminated polyamide is the polycondensation product of amino-acid withdicarboxylic acid, preferably C₄-C₁₄ amino-acid and preferably C₄-C₁₄dicarboxylic acid. More preferably, the carboxyl terminated polyamide isthe polycondensation product of amino-acid selected from the groupconsisting of 11-amino-undecanoic acid and 12-aminododecanoic acid, andmixtures thereof, with dicarboxylic acid selected from the groupconsisting of succinic acid, adipic acid, suberic acid, azelaic acid,sebacic acid, undecanedioic acid, dodecanedioic acid, terephthalic acid,and isophthalic acid, and mixtures thereof.

In another preferred embodiment, the carboxyl terminated polyamide isthe condensation product of a dicarboxylic acid and diamine. Preferably,the carboxyl terminated polyamide is the condensation product of aC₄-C₁₄ alkyl dicarboxylic acid and C₄-₁₄ diamine. More preferably, thepolyamide is selected from the group consisting of nylon6-6,6-9,6-10,6-12 and 9-6.

The invention is also directed to shaped articles comprising thepoly(trimethylene-ethylene ether)amide. Preferred shaped articlesinclude fibers, fabrics and films.

Polyurethanes and polyurethane ureas such as those described in U.S.patent application Ser. No. 10/215,575, filed Aug. 9, 2002 (published asUS 2004-0030060 A1), which is incorporated herein by reference, can beprepared with the poly(trimethylene-ethylene ether) glycols of theinvention as soft segments therein. Melt processable, and solutionprocessable polyurethanes and polyurethane ureas can be made frompoly(trimethylene-ethylene ether) glycol soft segment. Thesepolyurethanes and polyurethane ureas can be used as described therein.Poly(trimethylene-ethylene ether) based polyurethane ureas can be usedto make fibers by melt-spinning and other techniques.

Preferably, the poly(trimethylene-ethylene ether) glycol has a numberaverage molecular weight (Mn) of at least 250, preferably at least about500, more preferably at least about 1,000, even more preferably at leastabout 1,500 and most preferably about 2,000. The Mn is preferably up toabout 10,000, more preferably up to about 5,000, even more preferably upto about 4,000, yet even more preferably up to about 3,000, and morepreferably up to about 2,500.

The hydrophilic-lipophilic balance of thepoly(trimethylene-ethylene)glycol can be altered by changing theethylene glycol content in the polymer. In addition, the polymerlipophilic character can be increased by extracting the water solubleoligomer fraction from the polymer.

The polyurethane/polyurethane urea preferably comprises at least about90 weight %, more preferably greater than about 50 weight %, or greaterthan about 10 weight % soft segment.

Polyurethane prepolymers can be made by reactingpoly(trimethylene-ethylene ether) glycol with a diisocyanate. Forexample, they can be made by a process comprising:

-   -   (a) providing (i) diisocyanate and (ii)        poly(trimethylene-ethylene ether) glycol having a number average        molecular weight in the range of about 1,000 to about 5,000; and    -   (b) reacting the diisocyanate and the poly(trimethylene-ethylene        ether) glycol while maintaining an NCO:OH equivalent ratio of        about 1.1:1 to about 10:1 to form the diisocyanate-terminated        polyether-urethane prepolymer.

Polyurethane polymers can be made, for example, by a process comprising:

-   -   (a) reacting (i) diisocyanate and (ii)        poly(trimethylene-ethylene ether) glycol having a number average        molecular weight in the range of about 1,000 to about 5,000        while maintaining an NCO:OH equivalent ratio of about 1.1:1 to        about 10:1 to form diisocyanate-terminated polyether-urethane        prepolymer;    -   (b) reacting the diisocyanate-terminated polyether-urethane        prepolymer with diol chain extender at an OH:NCO mole ratio of        about 0.75:1 to about 1.15:1, or with diamine chain extender at        NH₂:NCO mole ratio of about 0.85:1 to about 1.10:1, to form the        polyurethane or the polyurethane-urea.

Preferably, the polyurethane or polyurethane-urea is cured.

According to another aspect, the polyurethane or polyurethane-urea canbe made by a process comprising:

-   -   (a) providing (i) diisocyanate, (ii) poly(trimethylene-ethylene        ether) glycol having a number average molecular weight in the        range of about 1,000 to about 5,000 and (iii) diol or diamine        chain extender; and    -   (b) reacting the diisocyanate, the poly(trimethylene-ethylene        ether) glycol, and the diol or diamine chain extender to form        the polyurethane or the polyurethane-urea.

According to yet another aspect, the polyurethane or polyurethane-ureacan be made by a process comprising:

-   -   (a) providing (i) diisocyanate-terminated polyether-urethane        prepolymer and (ii) diol or diamine chain extender; and    -   (b) reacting the diisocyanate-terminated polyether-urethane        prepolymer with the diol chain extender at an OH:NCO mole ratio        of about 0.75:1 to about 1.15:1, or with diamine chain extender        at NH₂:NCO mole ratio of about 0.85:1 to about 1.10:1, more to        form the polyurethane or the polyurethane-urea.

Preferably, the diol chain extender is selected from the groupconsisting of ethylene glycol, 1,2-propylene glycol, 1,3-propanediol,1,4-butanediol, 1,6-hexanediol, diethylene glycol,2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol,2,2-dimethyl-1,3-propanediol, 2,2,4-trimethyl-1,5-pentanediol,2-methyl-2-ethyl-1,3-propanediol, 1,4-bis(hydroxyethoxy)benzene,bis(hydroxyethylene)terephthalate, hydroquinonebis(2-hydroxyethyl)ether, and combinations thereof. Also preferably, thediamine chain extender is selected from the group consisting of1,2-ethylenediamine, 1,6-hexanediamine, 1,2-propanediamine,4,4′-methylene-bis(3-chloroaniline), dimethylthiotoluenediamine,4,4′-diaminodiphenylmethane, 1,3-diaminobenzene, 1,4-diaminobenzene,3,3′-dimethoxy-4,4′-diamino biphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl, 4,4′-diamino biphenyl, 3,3′-dichloro-4,4′-diamino biphenyl,and combinations thereof. Also preferably, the diisocyanate is selectedfrom the group 2,4-toluene diisocyanate, 2,6-toluene diisocyanate,4,4′-diphenylmethane diisocyanate, 4,4′-dicyclohexylmethanediisocyanate, 3,3′-dimethyl4,4′-biphenyl diisocyanate, 1,4-benzenediisocyanate, trans-cyclohexane-1,4-diisocyanate, 1,5-naphthalenediisocyanate, 1,6-hexamethylene diisocyanate, 4,6-xylyene diisocyanate,isophorone diisocyanate, and combinations thereof.

Preferably, the ratio of total reactive groups contained in thepoly(trimethylene-ethylene) ether glycol and chain extender componentsto the isocyanate groups is greater than 1. More preferably, the ratioof total reactive groups contained in the poly(trimethylene-ethylene)ether glycol and chain extender components to the isocyanate groups is0.8 to 1.

Optionally, the poly(trimethylene-ethylene ether) glycol is blended withother polyether glycol(s). Preferably, the poly(trimethylene-ethyleneether) glycol is blended with up to 50 weight % of other polyetherglycol.

Preferably, the other polyether glycol is selected from the groupconsisting of polyethylene glycol, poly(1,2-propylene glycol),polytrimethylene glycol, polytetramethylene glycol and combinationsthereof.

Preferably, the poly(trimethylene-ethylene ether) glycol comprises watersoluble and water insoluble chains. Preferably, the water soluble chainsare less than 1 wt % of total polymer. More preferably, the watersoluble chains are less than 0.5 wt % of total polymer.

The poly(trimethylene-ethylene ether) glycols of the present inventionhave a number of advantages. Poly(trimethylene-ethylene ether) glycolshave primary reactive hydroxyl groups to provide good reactivity towardsthe functional groups such as isocyanate or carboxylic acid or itsester. Poly(trimethylene-ethylene ether) glycols containing more than 10wt % ethylene oxide are completely amorphous and not crystallizable andthese are preferred for low temperature properties. The glycols areliquid at room temperature and have low viscosities, so they are easierto store, transport, and process compared to solid polyether glycols.Furthermore, for some applications requiring polyether glycols havingmore hydrophilic nature, the hydrophilic character ofpoly(trimethylene-ether) glycol can be altered by incorporating thedesired levels of ethylene oxide units in the polymer. Increasedhydrophilicity is expected to enhance the biodegradability of thepolyether glycol as well.

The poly(trimethylene-ethylene ether) glycols have very good propertiesfor use in thermoplastic elastomers. For instance, their reducedcrystallinity (as compared to the corresponding polytrimethylene etherglycols) provides a more amorphous character in the soft segments in thethermoplastic elastomers. In addition, they have increasedhydrophilicity. As a result, thermoplastic elastomers made with themwill have better breathability.

This invention allows the practitioner to alter the properties of thepolyether glycols significantly, giving the practitioner the ability totailor make polyethers glycols, particularly the ability to alter thedegree of crystallinity, crystallization kinetics, melting point andhydrophilicity, while still retaining the basic characteristics of thepolytrimethylene ether glycols. Most notably this can be done using anacid-catalyzed polycondensation which is efficient and convenient.

The invention is also very economical due to the ability to use theacid-catalyzed polycondensation process, and the greater availabilityand lower cost of ethylene glycol compared to 1,3-propanediol. Thepoly(trimethylene-ethylene ether) glycol of the present invention can bemade from the use of bio derived monomer such as 1,3-propanediol.

EXAMPLES

The following examples are presented for the purpose of illustrating theinvention, and are not intended to be limiting. All parts, percentages,etc., are by weight unless otherwise indicated.

In all the Examples, a commercial grade of 1,3-propanediol having apurity of >99.8% was used (available from DuPont). The ethylene glycolwas from Aldrich and had a purity of ˜98%.

The number-average molecular weights (Mn) of polyether glycol weredetermined either by analyzing end-groups using NMR spectroscopicmethods or by titration of hydroxyl groups.

Polydispersity (Mw/Mn) of the polymer was measured by GPC.

Melting point (T_(m)), crystallization temperature (T_(c)) and glasstransition temperature (T_(g)) were determined using the procedure ofthe American Society for Testing Materials ASTM D-3418 (1988) using aDuPont DSC Instrument Model 2100 (E. I. du Pont de Nemours and Co.,Wilmington, Del. (“DuPont”)), according to the manufacturer'sinstructions. The heating and cooling rates were 10° C. per minute.

ASTM method D445-83 and ASTM method D792-91 were used to determine theabsolute (dynamic) viscosity and density of the polymer, respectively.

Example 1

Poly(trimethylene-ethylene ether) glycol was prepared from1,3-propanediol (86 mole %) and ethylene glycol (14 mole %) as follows:

135g (1.78 moles) of 1,3-propanediol and 18 g of ethylene glycol (0.29mole, corresponding to 14 mole %) were charged into a 250-mL 4-neckflask that was equipped with a glass shaft, a nitrogen inlet connector,and a port for a thermal couple. The mixture was purged with nitrogen(0.15 L/min) for 5 minutes under ambient temperature and pressure. 1.53g of concentrated sulfuric acid was slowly added to the mixture at roomtemperature. The reactor was operated under atmospheric pressure andnitrogen atmosphere at 170° C. for 13 hours. 34 ml of distillate (mostlywater) was collected at the end of the run. After polymerization, 121 gof distilled water was charged into the crude polymer that was thenstirred for 4 hrs at 100° C. under nitrogen atmosphere. Most of the acidpresent was extracted after cooling the mixture to 35° C. to 40° C., andseparating the aqueous layer from the polymer phase. The residual acidpresent in the polymer was neutralized with Ca(OH)₂ (0.01 g) slurry at60° C. for 2 hours under nitrogen atmosphere. The copolymer was dried toremove residual water present using a rotovap under 29 in-Hg pressureand 100° C. temperature. Finally, the dried polymer was filtered hotthrough a precoated 1 μm Whatman filter paper. The polymer propertiesare reported in Table 1.

Example 2

Poly(trimethylene-ethylene ether) glycol was prepared from1,3-propanediol (95 mole %) and ethylene glycol (5 mole %) as follows:

Example 1 was repeated by varying the amount of 1,3-propanediol (149.1g), ethylene glycol (6.40 g, corresponding to 5 mole %) and 1.55 g ofsulfuric acid.

Example 3

Poly(trimethylene-ethylene ether) glycol was prepared from1,3-propanediol (70 mole %) and ethylene glycol (30 mole %) as follows:

Example 1 was repeated by varying the amount of 1,3-propanediol (109.9g), ethylene glycol (38.4 g, corresponding to 30 mole %) and of sulfuricacid (1.48 g).

Example 4

Poly(trimethylene-ethylene ether) glycol was prepared from1,3-propanediol (70 mole %) and ethylene glycol (30 mole %) as follows:

Example 3 was scaled up in a 5-L reactor. 2197.2 g (70 mole %) of1,3-propanediol and 768.2 g (30 mole %) of ethylene glycol were chargedinto the reactor. 29.69 g (1 wt % of total raw material) of sulfuricacid was added. The polymer properties are reported in Table 1.

Example 5

Example 3 was repeated except the polymerization temperature wasmaintained at 160° C. for 35 hours. The polymer properties afterpurification are reported in Table 1.

Example 6

Poly(trimethylene-ethylene ether) glycol was prepared from1,3-propanediol (70 mole %) and ethylene glycol (30 mole %) in a 20 Lreactor as follows:

8.81 kg of 1,3-propanediol, 3.081 kg of ethylene glycol and 0.109 kg ofconcentrated sulfuric acid were charged into the reactor. The mixturewas purged with nitrogen gas for 30 minutes and the reaction mixture washeated to 160° C. The polymerization reaction was continued for 25 hoursat inert atmospheric pressure while collecting the water of reaction.The polymer properties are reported in Table 1.

Example 7

In this experiment, poly(trimethylene-ethylene ether) glycol wasprepared in a semi-batch process by adding ethylene glycol (30 mole %)dropwise into 1,3-propanediol (70 mole %) as follows:

109.3 g (1.78 moles) of 1,3-propanediol was charged into a 250-mLreactor that has similar setup to the one in Example 1. The1,3-propanediol was purged with nitrogen at 0.15 L/min for 10 minutes atambient temperature and pressure. 1.49 g of concentrated sulfuric acidwas added dropwise to the 1,3-propanediol. The mixture was heated undera nitrogen blanket to 170° C. Once the 160° C. temperature was reached,ethylene glycol addition was started at rate of 1 drop/9 seconds overthe course of 2 hours. The polymerization was conducted for 12 hours at170° C. and atmospheric pressure. 34 ml of distillate was collected atthe end of the end of 12 hrs. Purification steps followed Example 1. Thepolymer properties are reported in Table 1.

Comparative Example A (Control)

Polytrimethylene ether glycol was prepared by repeating Example 1without using ethylene glycol.

Example 8

Example 3 was repeated with diethylene glycol by replacing ethyleneglycol as follows: 109.9 g of 1,3-propanediol, 65.7 g of diethyleneglycol and 1.77 g of concentrated sulfuric acid were charged into a 250mL reactor. The polymerization was carried out 170° C. under nitrogen.After 6 hours, the reaction mixture turned dark brown and theexperimental run was stopped. During 6 hours of the reaction, 89.2 mL ofdistillate was collected and the distillate contained significant amountof organics besides water as determined by the refractive index of thedistillate indicating formation of cyclic dioxane from diethyleneglycol.

Example 9

Block poly(trimethylene-ethylene ether) glycol was prepared from1,3-propanediol (90 mole %) and polyethylene glycol (Mn=400, 10 mole %)as follows: 70.6 g (0.93 moles) of 1,3-propanediol and 41.4 g ofpolyethylene glycol (0.103 mole, corresponding to 10 mole %) werecharged into a 250 mL reactor equipped with a glass shaft, a nitrogeninlet connector, and a port for a thermal couple. Nitrogen was purgedthrough the mixture at a flow rate of 0.15 L/min for 10 minutes underambient temperature and pressure. 1.1360 g (1 wt %) of concentratedsulfuric acid was added at 120° C. The polymerization was carried out at160° C. for ˜1 h and at 170° C. for 12 h under nitrogen. 20.0 ml ofdistillate was collected at the end of the run.

After polymerization, 92 g of distilled water was charged into the crudepolymer that was then stirred for 4 hrs at 100° C. under a nitrogenblanket. Most of the acid present was extracted after cooling themixture to 45° C. to 50° C. and separating the aqueous layer from thepolymer phase. The crude polymer was charged again with 92 g ofdistilled water and stirred for 1 h at 100° C. under a nitrogen blanket.After cooling the mixture, the two layers were separated. The residualacid present in the polymer was neutralized with Ca(OH)₂ (0.0634 g)slurry at 60° C. for 2 hours under nitrogen atmosphere. The copolymerwas dried to remove residual water present using a rotovap under 29in-Hg pressure and 100° C. temperature for 3 h. Finally, the driedpolymer was filtered hot through a precoated 1 μm Whatman filter paper.The block copolymer molecular weight was determined from NMR and foundto be 2110.

The polymers and their properties are compared in the following table.

TABLE 1 Properties of Poly(trimethylene-ethylene ether) glycols Ethyleneglycol Mn Mn Tm, Tc, Tg, Viscosity at Example mole % (NMR) (Titration)Mw/Mn ° C. ° C. ° C. 40° C., cP 1 14 1,889 1,847 1.64 None None −75 5302 5 2,262 — 1.59 1.5, 6.9 −17 −75 790 3 30 1517  1521 1.63 None None −75280 4 30 1245 — 1.60 None None −75 — 5 30 2223 — — None None −75 — 6 301385 — 1.56 None None −75 277 7 30 1810  1823 1.64 None None −75 420 A1,858 1,910 1.61 20 −37 −75 530 (Control)

As shown in the Table, the Tg and polydispersity of thepoly(trimethylene-ethylene ether) glycols are in the same range of thepolytrimethylene ether glycol and the viscosity of the copolyetherhaving molecular weight 1847 is about the same with the homopolymer;however, the melting point and crystallization temperatures of thepoly(trimethylene-ethylene ether) glycols differed significantly fromthe polytrimethylene ether glycol.

The foregoing disclosure of embodiments of the present invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. Many variations and modifications of the embodimentsdescribed herein will be obvious to one of ordinary skill in the art inlight of the disclosure.

1. A poly(trimethylene-ethylene ether) glycol prepared by acid catalyzedpolycondensation of about 95 to about 99 mole % 1,3-propanediol reactantand about 5 to about 1 mole % ethylene glycol reactant.
 2. Thepoly(trimethylene-ethylene ether) glycol as claimed in claim 1, whereinthe polycondensation is carried out with an acid polycondensationcatalyst comprising sulfuric acid.
 3. The poly(trimethylene-ethyleneether) glycol as claimed in claim 1, prepared by acid catalyzedpolycondensation of 1,3-propanediol reactant and ethylene glycol.
 4. Thepoly(trimethylene-ethylene ether) glycol as claimed in claim 2, preparedby acid catalyzed polycondensation of 1,3-propanediol reactant andethylene glycol.
 5. The poly(trimethylene-ethylene ether) glycol ofclaim 1, wherein the 1,3-propanediol reactant is seledted from the groupconsisting of 1,3-propanediol, and oligomers of 1,3-propanediol having adegree of polymerization of 2 to 3, and mixtures thereof.
 6. Thepoly(trmethylene-ethylene ether) glycol of claim 1, wherein the ethyleneglycol reactant is selected from the group consisting of ethyleneglycol, and oligomers of ethylene glycol. having a degree ofpolymerization of 3 to 4, and mixtures thereof.
 7. Thepoly(trimethylene-ethylene ether) glycol of claim 5, wherein theethylene glycol reactant is selected from the group consisting ofethylene glycol, and oligomers of ethylene glycol having a degree ofpolymerization of 3 to 4, and mixtures thereof.
 8. Thepoly(trimethylene-ethylene ether) glycol of claim 5, wherein the1,3-propanediol reactant is 1, 3-propanediol.
 9. Thepoly(trimethylene-ethylene erher)glycol of claim 8, wherein the1,3-propanediol is derived from a renewable source.
 10. Thepoly(trimethylene-ethylene ether) glycol of claim 6, wherein theethylene glycol reactant is ethylene glycol.
 11. Thepoly(trimethylene-ethylene ether) glycol of claim 8, wherein theethylene glycol reactant is ethylene glycol.
 12. Thepoly(trimethylene-ethylene ether) glycol of claim 1, having a numberaverage molecular weight (Mn) of 250 to about 10,000.
 13. Thepoly(trimethylene-ethylene ether) glycol of claim 1, having a numberaverage molecular weight (Mn) of about 1,000 to about 5,000.